Running a car on a hoist is always a dangerous situation but at times its the only way to find the issue. If the car can be lifted and secured to the lift itself with straps, that is a better situation. Have you checked the CV joints on the axles themselves? I would give a call to Jack Sharkey at Pantera of Miami and ask him his thoughts or anyone else you know that sees a large number of cars. Owners usually do have answers but Jack may of seen this before and cut a large amount of trouble shooting for you. Again, I would try the running on a lift myself if I can't find someone with input but make sure before going under that the car is secure incase of any sudden movement or violent vibration that could shift the car. Just my .02 This hobby is very fun make sure you are around to enjoy it!
Good Luck